Commencement of 7 minute period

The commencement of the 7 minute period (referred to on the previous page) is determined as follows:

 

 

 

 

In the event of communication failure, REMEMBER: · Follow the ASSIST code of practice A 'Acknowledge' - S 'Separate' - S 'Silence' - I 'Inform' - S 'Support - T 'Time' (See the ASSIST panel on the bottom left for further information.)

· INFORM your Supervisor · as soon as the failure becomes known, maintain separation between the affected ACFT and other ACFT based on the assumption that yhe ACFT will operate in accordance with the (ICAO) rules define for VMC or for IMC   · recognise that this is an unusual situation which could become an emergency · establish whether the aircraft has: o functioning transmitter o functioning receiver o neither

· if blocked frequency, establish the source: o ground o airborne · inform all units concerned · try to make contact with the aircraft on other available frequencies - 121.5Mhz; 243.0 MHz; company frequency, or by any other available means, eg SELCAL; VOR; mobile phone etc · if control has to be transferred to another ATC station, radar hand-off procedure should be followed

 

 

 

PRESSURISATION PROBLEMS:

 

A failure of the cabin pressurisation system causes an immediate danger to the aircraft, crew and passengers. This is an emergency situation.

 

 

During high level flight, the aircraft cabin is pressurised in order to provide air for breathing and a comfortable environment for the human body.

Engine bleed air is conditioned (cooled down and mixed with outside air) and guided into the cabin. The amount and pressure of the conditioned air is regulated by a computer and outflow valves.

Pressurisation problems may be caused by:

· malfunction of the pressure outflow

· a malfunction of the pressure regulating valves

· a physical leak in the system

· damage to a door or window

A rapid decompression in the cabin leads to loss of oxygen and
increased gas pressure in the human body.

 

The drop in pressure will result in a sudden temperature drop, fog and reduced visibility in the cabin.

The difference in air pressure between
inside and outside of the cabin leads to a wake effect
where the wind sucks items towards the hole.

Loose objects will fly through the cabin
and may harm passengers and crew.

Urns may boil over and bottles burst.

 

 

When the air from the cabin is lost, the time of useful consciousness (TUC) is short. This is the period of time during which a person can continue to function "normally", without oxygen, before "blackout" occurs.

 

 

The time of useful consciousness can vary from 4 to 30 seconds depending on:

· the altitude

· the size of the leak

· the size of the fuselage

It is vital that oxygen masks are deployed for pilot, crew, and passengers during the TUC. The crew immediately puts on oxygen masks and then assists passengers to do the same.

The pilot can no longer use the standard headset for RTF communication. The pilot's mask is therefore equipped with a microphone, and the earpiece is automatically switched over to a cabin loudspeaker.

 

 

 

 

 

 

In the event of pressurisation problems, REMEMBER:

Follow the ASSIST code of practice:

A 'Acknowledge' - S 'Separate' - S 'Silence' -
I 'Inform' - S 'Support - T 'Time'

(See the ASSIST panel on the bottom left for further information.)

· Clear airspace directly beneath the aircraft